Pipe joint

Abstract

An annular sealing material seals a pipe joint between a socket and a spigot. The sealing material includes a bulb part which is composed of a first bulb, a second bulb located closer to the inner side of the socket than the first bulb, and a narrow part present between the first and second bulbs. The first bulb is pressed against the inner circumferential surface of the socket. The second bulb is pressed against the outer peripheral surface of the spigot. The second bulb is inclined towards the pipe center from the first bulb in a natural state before it is provided between the socket and the spigot. The inner diameter of the second bulb is smaller than the outer diameter of the spigot in the natural state. The second bulb is extensible in the pipe diameter direction due to elastic deformation of the narrow part.

The invention claimed is: 
     
       1. A pipe joint in which a spigot formed at an end of one pipe is inserted into a socket formed at an end of another pipe, the pipes being joined to each other,
 the pipe joint comprising: 
 a lock ring accommodating groove formed on an inner circumference of the socket; 
 a lock ring accommodated in the accommodating groove and singularly divided in a circumferential direction; 
 an annular centering member disposed between an inner circumferential surface of the accommodating groove and an outer peripheral surface of the lock ring, for holding the lock ring centered with respect to the socket when the spigot is not inserted into the socket; and 
 a protrusion which is formed on an outer periphery of a distal end of the spigot, is capable of elastically pushing out the lock ring accommodated in the accommodating groove with the spigot inserted into the socket in a pipe diameter direction to pass through an inner circumference side of the lock ring, and is capable of being engaged with the lock ring from an inner side of the socket when a detachment force is applied in a pipe axial direction between the socket and the spigot joined to each other to prevent the spigot from being detached from the socket, 
 the centering member including a plurality of divided parts in a pipe circumferential direction, and a connecting part connecting the adjacent divided parts in the pipe circumferential direction, 
 the divided part including a holder holding the lock ring from an outer peripheral side, and a hold width protruding inward in the diameter direction from a socket inner side portion of the holder so as to be engaged with the lock ring in the pipe axial direction, wherein 
 the connecting part is disposed closer to an outer peripheral side than the divided parts and is elastically deformable in the pipe diameter direction in response to the elastically pushed-out lock ring. 
 
     
     
       2. The pipe joint according to  claim 1 , wherein the connecting part is arc-shaped, and one end and another end of the arc are connected respectively to the pair of adjacent divided parts in the pipe circumferential direction. 
     
     
       3. The pipe joint according to  claim 1 , wherein an inner circumferential protrusion for forming the lock ring accommodating groove is formed closer to the inner side of the socket than the lock ring accommodating groove, and in the divided part, the hold width protrudes more inward in the pipe diameter direction than the inner circumferential protrusion when the holder holds the lock ring from the outer peripheral side before the spigot is inserted into the socket. 
     
     
       4. An annular centering member in a pipe joint in which a spigot formed at an end of one pipe is inserted into a socket formed at an end of another pipe, the pipes being joined to each other, the centering member being disposed between an inner circumferential surface of a lock ring accommodating groove formed on an inner circumference of the socket and an outer peripheral surface of a lock ring accommodated in the accommodating groove and singularly divided in a circumferential direction, for holding the lock ring centered with respect to the socket when the spigot is not inserted into the socket,
 the spigot including a protrusion on an outer periphery of the spigot, wherein 
 the protrusion is capable of elastically pushing out the lock ring accommodated in the accommodating groove with the spigot inserted into the socket to pass through an inner circumferential side of the lock ring, and is capable of being engaged with the lock ring from an inner side of the socket when a detachment force is applied in a pipe axial direction between the socket and the spigot joined to each other to prevent the spigot from being detached from the socket, 
 the centering member includes a plurality of divided parts in a pipe circumferential direction and a connecting part connecting the adjacent divided parts in the pipe circumferential direction, 
 the divided part includes a holder holding the lock ring from an outer peripheral side, and a hold width protruding inward in the diameter direction from a socket inner side portion of the holder so as to be engaged with the lock ring in the pipe axial direction, and 
 the connecting part is disposed closer to an outer peripheral side than the divided parts and is elastically deformable in the pipe diameter direction in response to the elastically pushed-out lock ring.